774 



NATURE 



[February io, 192 i 



in a leaf, it was necessary to find some other sub- 

 stance which would serve the purpose, and lead 

 chromate was found to be very suitable. The formulae 

 used are given and also the cost of each and of the 

 spraying. Samples from the cortrol and sprayed 



plots were tested by tea-brokers, and their reports are 

 fjiven, the tea treated with the sprays, especially that 

 containing resin and sodium carbonate, in addition to 

 lead chromate, being generally preferred. Rain was 

 found to have little effect, provided the spray had dried. 



Food and its Preservation.' 



THE work done under the direction of the Food 

 Investigation Board of the Department of 

 Scientific and Industrial Research during the year 

 1919, although its primary object may be said to 

 have been of a practical nature and mainly devoted 

 to the various means of preserving animal and vege- 

 table food, serves well to show how such an object 

 requires previous investigation of many fundamental 

 and purely scientific problems. On account of the 

 strictures that have been made as to the support of 

 pure science by the Department in question, we may 

 take note that it is pointed out in the report before 

 us that "the application to industry of many of the 

 researches is not immediate, and often not obvious." 

 Such results will be especially referred to in the course 

 of this article, but it is not intended thereby to mini- 

 mise the value of the practical work of the Board. 



With regard to the freezing of meat and fish, a 

 valuable series of researches was undertaken on tlie 

 phenomena occurring in the freezing and thawing of 

 systems containing colloids and electrolytes, with 

 especial reference to the separation of the con- 

 stituents of such systems and to the diffusion of 

 salts through their solid phases. Our knowledge of 

 the properties of these systems has been greatly 

 enlarged by this work, and a general report on it is 

 now being prepared. Attention may be particularly 

 directed to the fact that by sufficiently rapid cooling 

 to a temp)erature which corresponds to the eutectic 

 of a saline solution the separation of frozen water as 

 a visible phase is avoided. Thus, on thawing, the 

 system returns to its original state and the irreversible 

 separation of the colloidal material does not take 

 place, as happens on slow freezing at a temperature 

 onlv a few degrees below the freezing point of the 

 svstem. 



The conditions of growth oj bacteria and moulds 

 were naturallv subjects of immediate interest. It is 

 well known that bacteria growing in a particular 

 medium, after a period of multiplication, gradually 

 die off. This is shown by Dr. Graham-Smith, in the 

 report, to be due, not to accumulation of toxic pro- 

 ducts of their own activity, but to the exhaustion of 

 some specific food material. Bacteria of another 

 species are able to grow in a medium which has 

 previously been exhausted by a different species so 



far as its own growth is concerned. An interesting 

 fact brought out by researches on the "black-spot" 

 mould (shown to be a species of Cladesporium) is 

 that it will grow at a temperature of —5"^ C. It is 

 clear that the protoplasm in the cells does not freeze, 

 although the e.xpressed juices of plants usually freeze 

 between —2° and —3° C. No doubt capillary forces 

 are responsible for the lowering of the freezing point 

 in the narrow cells. 



The question of the discoloration of fruit led to 

 an investigation on the nature of the enzymes respon- 

 sible for oxidation in plants. An important fact in 

 relation to the general theory of the mechanism of 

 oxidation was brought out in an examination of 

 linseed oil. It was found that the oil oxidises slowly 

 in air without the presence of any kind of catalyst, 

 although in the oxidation system of the cell there 

 is evidence of the presence of a catalyst accelerating 

 autoxidation. In connection with enzymes the work 

 on pectin production may be mentioned. 



Of more strictly chemical interest is the discovery 

 that glycerol can be replaced in fats by mannitol, 

 such fats being similar to the corresponding glycerol 

 esters and behaving in the same way as foods. Other 

 work giving an insight into the chemistry of the 

 production of glycerol itself was also undertaken. 

 Of practical importance for workers with the products 

 of degradation of proteins is the method devised by 

 Mr. Foreman for estimating the simpler products of 

 bacterial decomposition. A curious fact is that the 

 equilibrium position reached in the autolysis of beef 

 is not the same as that in the case of mutton, sug- 

 gesting that the presence of more than one phase in 

 the heterogeneous system of the cell must be taken 

 into consideration. 



The work of the Engineering Committee of the 

 Board, as would be expected, has been mainlv indus- 

 trial, but the systematic investigation of the heat- 

 flow through various materials and the loss of heat 

 by convection from plane surfaces may be referred to 

 here as of general scientific interest. 



We mav note, finally, that the Board has obtained 

 a grant to build and equip a research station at Cam- 

 bridsje for biochemical and biophysical investigations 

 at low temperatures. 



W. M. B. 



The Older Palaeolithic Age in Egypt. 



PROF. C. G. SELIGMAN, at a meeting of the 

 Royal Anthropological Institute on January 11, 

 read an important paper on " The Older Palaeolithic 

 Age in Egypt," embodying the results of an attempt 

 made in 1914 to secure definite stratigraphical 

 evidence of the antiquity of implements which, if 

 found in Europe, would be classed as Chcllean, 

 Acheulean, or Mousterian. The sites visited were 

 Abydos, Thebes, Tel-el-.\marna, Meir, and Wady 

 Sheikh, and a short trip was made to the Fayum. 

 Some areas, however, may be described as flintless; 



* Department of Scientific and Industrial Research. Report of the Food 

 Investigation Board for the Year 1919. Pp. 36. (London: H.M. Stationery 

 Office.) Price 6</. net. 



NO. 2676, VOL. 106] 



flints of Palaeolithic type were very common in the 

 neighbourhood of Thebes and .Abydos, but were scarce 

 near Meir and Tel-el-.\marna, and did not include 

 either Chellean or .Acheulean types. Wady Sheikh 

 showed no definite Palaeolithic types, but speci- 

 mens of early historic date were valuable for the 

 light thev threw on the patination of high desert 

 specimens. 



The implements found included hand-axes (Chellean 

 tvpe), hand-axes with borer point (not found in 

 Europe), and finelv w-orked ovates (Acheulean type). 

 The points, side scrapers, borers, hollow scrapers, 

 and tanged points (spear- or arrow-heads) Prof. Selig- 

 man grouped together as Mousterian, not because 



